Composite steel truss and precast concrete slab and beam units



Aug. 27, 1968 p. uss 3,398,498

COMPOSITE STEEL TRUSS AND PRECAST CONCRETE SLAB AND BEAM UNITS 2Sheets-Sheet 1 Filed Sept. 9, 1966 "Warren PAUL KRAUSS Aug. 21, 1968 P.KRAUSS 3,398,498

COMPOSITE STEEL TRUSS AND' PRECAS'I CONCRETE SLAB AND BEAM UNITS FiledSept. 9, 1966 2 Sheets-Sheet 2 \xmsxm xxx I INVINTOR PAUL KRAUSS @g ziwUnited States Patent F 3,398,498 COMPOSITE STEEL TRUSS AND PRECASTCONCRETE SLAB AND BEAM UNITS Paul Krauss, Winnipeg, Manitoba, Canada,assignor to Barkrauss Enterprises Ltd., Winnipeg, Mamtoba, Canada FiledSept. 9, 1966, Ser. No. 578,341 8 Claims. (Cl. 52-691) ABSTRACT OF THEDISCLOSURE A composite concrete and steel truss consisting of areinforced concrete slab or beam with a plurality of downwardlydepending webs and a number of exposed steel members. The steel membersincorporated with the concrete slab and webs produce a composite trussunit in which the steel members are the tension chord and tensiondiagonals and the concrete slab and vertical webs are the compressionmembers.

This invention relates to new and useful improvements in composite steeltruss and precast concrete slab and beam units.

The invention consists primarily of a precast concrete slab having acentral longitudinally extending concrete member upon the undersidethereof and a plurality of downwardly depending, substantiallyrectangular webs. Incorporated with the structure and precast therewithis an arrangement of steel tension bars, the principal ones extendingfrom end to end of the truss and engaging the lower edges of the webs.Secondary reinforcing extends from the lower edges of some of the webs,diagonally upwardly into the aforementioned longitudinal member.

Open web, steel joist floors are normally used in construction and5115561 from several disadvantages.

Such disadvantages include poor load distribution transverse to thejoist span and subsequent poor resistance to concentrated loads such aspartitions, ofiice machines, and the like.

Another disadvantage is light weight and poor transverse loaddistribution which results in a very low vibration resistance to thestructure.

Such open web steel joist floors usually include a relatively thin 2"poured concrete floor slab which is poured in situ, and is thereforevery much subject to shrinkage, cracking, premature drying andsubsequent dusting.

Furthermore the curing of thin slabs also presents a considerableproblem both in summer and winter weather.

The conventional open web steel joist floor includes the joist seat andslab, the total depth of which conventionally are approximately 4 /2".Unfortunately this is neither a modular brick nor block dimension and istherefore awkward in bearing wall construction.

The use of steel joists over crawl spaces is not recommended unlessexpensive rust protection is carried out. The thin wall rolled chordsections, high stress steel, and fusion welded web connections combinedare easily subject to corrosion.

Todays open web steel joists are mass produced, using electric fusionwelding. Therefore quality control is difficult and defects, such aspoor or broken welds, occur frequently.

The installation of duct work transverse to steel joists within thejoist space is difiicult due to frequent occurrence of joist web membersnecessary for strength characteristics.

Finally, fire resistance of the floor can only be achieved by theinstallation of a fire resistant ceiling therebelow.

The above disadvantages are largely counteracted by the presentinvention inasmuch as the concrete compression verticals of the trusssystem are carried out as reinforced Patented Aug. 27, 1968 slabs. Afterinstallation of the floor system, these slabs act as continuousdistribution members and by modification of the reinforcing andconnections, full 2-Way load distribution can be achieved.

The relatively deep concrete bridging beams hereinafter to be described,greatly increase the vibration resistance of the floor and the factorycontrolled precast concrete slab and the longitudinal compression in theslab due to truss action will result in a crack free floor.

The present slab system hereinafter to be described, lends itself towinter construction because all structural field connections are weldedor bolted and the grouting of joints can be carried out after thebuilding is closed in and heated.

The dimensions of the present device include the seats of the slab whichhave a depth of one standard concrete block and therefore will replace afull block course during the building operation. The 7%" depth of theseat and the beam depth under the slab can be maintained for any spanlength.

The truss tension chords consist of plain round solid bars which do nottend to collect dust and corrosive moisture. Inasmuch as no welding isused in the manufacture of the truss, the bars can be precoated for rustresistance.

No structural welding is used in the fabrication of the slab units andtherefore quality control regarding structural strength is dependent onconcrete control only, a well known and simple standard procedure.

The construction permits air ducts of considerable size to be installedin both directions. By leaving the diaphragms or webs solid, air returnplenums may be created by simply closing the bottom of the passagesdefined by the plurality of webs.

With little additional cost, built in concrete ducts can be provided forfloor electrification purposes.

The use of open web composite floor beams as shown, will permit ductwork installation completely within the floor construction and the fireresistance of the slabs and beams can easily be achieved by concrete orplaster coating of exposed steel tension members.

With the foregoing in view, and all those objects, purposes oradvantages which may become apparent from consideration of thisdisclosure and specification, the present invention consists of theinventive concept embodied in the method, process, construction,arrangement of parts, or new use of the same, as herein particularlyexemplified in one or more specific embodiments of such concept,reference being had to the accompanying figures in which:

FIGURE 1 is a side elevation showing a four panel truss.

FIGURE 2 is an underside isometric view of the four panel truss shown inFIGURE 1.

FIGURE 3 is an end elevation, on reduced scale, showing a section oferected truss slabs.

FIGURE 4 is an enlarged cross sectional view substantially along theline 44 of FIGURE 1.

FIGURE 5 is a section substantially along the line 55 of FIGURE 1.

FIGURE 6 is a section substantially along the line 6-6 of FIGURE 4.

FIGURE 7 is a section substantially along the line 77 of FIGURE 5.

In the drawings like characters of reference indicate correspondingparts in the different figures.

Proceeding therefore to describe this invention in detail, referenceshould be made to the accompanying drawings which show the panel truss.

It will, of course, be appreciated that the panel truss is cast in anupside down position within a mould (not illustrated) for ease ofmanufacture.

The truss illustrated in FIGURES 1 to 5 inclusive comprises a relativelythin upper rectangular slab including conventional reinforcing wires 11and 11'.

At either end of the panel 10 are cast in place end seats 12 by whichthe slabs may be supported upon building walls.

Depending downwardly from the underside 13 of the panel 10 is aplurality of webs or diaphragms 14 substantially rectangular when viewedin section, these webs or diaphragms are precast and set in place andbeing reinforced by reinforcing wires or rods 15 and 15'. Rods 15 arediagonally situated and rods 15 are substantially open rectangular, theupper sides of which extend into the center line of the panel 10.

It is desirable to leave a cylindrical aperture 16 one upon each side ofthe diaphragm but, if desired, these may be closed.

Extending longitudinally upon the center line of the panel and upon theunderside thereof is the main concrete rib or longitudinal member 17also cast in place, which not only acts as a strengthening rib or beambut also as a retaining anchor for the tension rods or memberscolectively designated 18.

The main tensioning rods specifically designated 19 comprise a pair ofspaced and parallel, rolled steel rods, the ends 20 of which inclineupwardly through the ends 21 of the main ribs 17 and hook downwardly asat 22, within the seats 12 thus anchoring these rods securely within thetruss.

The major portions 23 of these rods engage the under side edges 24 ofthe diaphragms as clearly shown in the drawings and are Welded tobearing plates 25 within the underside edges 24, said arrangement beingshown in FIGURE 4.

A secondary reinforcing rod or load transfer member 26 is securedcentrally of the rods 19, to the plates 25 of the central Web ordiaphragm and the portion 27 of this rod extends diagonally upwardlyinto the main rib 17 and then hooks downwardly as at 28 in order to beanchored within this rib adjacent the webs or diaphragms upon eitherside of the central web or diaphragm.

FIGURES 1 and 2 show a four panel truss slab which has just beendescribed but it will be appreciated that a six panel truss can beformed in which the reinforcing bars are similarly arranged, there beingadditional secondary bars 26 upon each side of the center of the trussslab.

Also cast in place within the flanges, webs or diaphragms 14, arewelding plates 29 secured to hook anchors 30 and these Welding platesare flush with the surface of the side edges 31 of the diaphragm 14.

When the truss slabs are placed upon the supporting walls in side 'byside relationship as shown in FIGURE 4, adjacent slabs may be levelledby jacking and then the slabs may be welded together at the diaphragmsby means of the plates 29 of adjacent diaphragms which are ininterfaci-al contact.

This gives an extremely smooth and level floor surface which does notrequire the conventional floor topping.

It will be noted that the longitudinal edges of the upper panel 10 areprovided with longitudinal recesses 32 (see FIGURE 5) and these groovesmay be grouted when the welding has been completed.

Various modifications can be made within the scope of the inventiveconcept disclosed. Accordingly, it is intended that what is describedherein should be regarded as illustrative of such concept and not forthe purpose of limiting protection to any particular embodiment thereof, but that only such limitations should be placed upon the scope ofprotection to which the inventor hereof is entitled, as justicedictates.

What I claim as my invention is:

1. A composite steel truss and precast concrete slab and beam unitcomprising in combination a substantially elongated rectangular upperconcrete slab, longitudinally and transverse extending steel reinforcingin said slab, a slab seat formed on each end of said slab and dependingdownwardly therefrom; a plurality of transverse concrete webs formedintegrally with and depending downwardly from the underside of said slabat intervals along the length thereof, and at least one steel tensionmember secured intermediate the ends thereof to the base of at least oneof said webs, the ends of said tension member inclining upwardly towardsthe ends of said slab and being secured to said slab, said tensionmember extending longitudinally of said slab, and at least one secondarytension member secured intermediate the ends thereof to one of saidwebs, the ends of said secondary tension member also inclining upwardlytowards the ends of said slab and being secured to said slab inboard ofthe ends thereof.

2. The device according to claim 1 which includes a longitudinallyextending beam formed integrally with said slab and said webs and uponthe underside of said slab, said beam connecting with said seats at eachend thereof.

3. The device according to claim 1 in which said webs include a pair ofdiagonally situated reinforcing rods and a pair of open rectangularreinforcing rods.

4. The device according to claim 2 in which said webs include a pair ofdiagonally situated reinforcing rods and a pair of open rectangularreinforcing rods.

5. The device according to claim 1 in which each web is provided withwelding plates embedded therein, hook anchors secured to said weldingplates and extend inwardly into said web, one side of said welding platebeing flush with the side edges of said webs whereby adjacent weldingplates of adjacently situated slabs may be welded together to form anintegral structure.

6. The device according to claim 2 in which each web is provided withwelding plates embedded therein, hook anchors secured to said Weldingplates and extend inwardly into said web, one side of said welding platebeing flush with the side edges of said webs whereby adjacent weldingplates of adjacently situated slabs may be welded together to form anintegral structure.

7. The device according to claim 3 in which each web is provided withwelding plates embedded therein, hook anchors secured to said weldingplates and extendinwardly into said web, one side of said welding platebeing flush with the side edges of said webs whereby adjacent weldingplates of adjacently situated slabs may be Welded together to form anintegral structure.

8. The device according to claim 4 in which each web is provided withwelding plates embedded therein, hook anchors secured to said weldingplates and extend inwardly into said web, one side of said welding platebeing flush with the side edges of said webs whereby adjacent Weldingplates of adjacently situated slabs may be Welded together to form anintegral structure.

References Cited UNITED STATES PATENTS 1,572,669 2/1926 Muller 52-7232,154,619 4/1939 Hurley 52587 2,813,310 11/1957 Harrison 52-2262,912,849 11/ 1959 Wissinger 52-723 FOREIGN PATENTS 464,361 4/ 1937Great Britain. 1,018,618 10/1952 France.

FRANCIS K. ZUGEL, Primary Examiner.

